Decoration of objects by hot-stamping or in mould decoration proceeds by applying, under pressure and/or heat, a foil carrying a coloured layer that is transferable by heat and pressure. In many applications the foil carries a uniform coloured layer. The object is decorated by pressing the foil against the object with an image bearing stamper. This latter kind of process creates a lot of wasted colour since only a small part of the coloured layer is transferred.
Printing colour images on transfer foils by electro(stato)graphic means is well known in the art. The advantage of electro(stato)graphic methods, for making such images, over traditional printing techniques (offset, screen-printing, etc.) is the simplicity of the electro(stato)graphic system, the price and, when using dry electrostatic printing, the fact that the preparation of such transfer foils can be used with very little impact on the environment. Moreover the electro(stato)graphic methods make it possible to make transfer images in small edition and even to personalise the images. Also the fact that electro(stato)graphic imaging methods are often digital printing methods present an advantage over the printing methods that are traditionally used for making images transferable by hot stamping or in-mould decoration.
In DE-A-27 27 223 a method for transferring images onto cotton T-shirts by first producing an electrostatic latent image in a known manner on an intermediate substrate, coating the latent image with thermoplastic toner, reversing the polarity of charge to transfer the toner image to a second intermediate substrate coated on both sides with a layer (preferably of polyethylene) and a thermoplastic clear lacquer layer adjacent the toner image. The toner image fixed on the substrate is transferred to the T-shirt by application of heat and pressure.
In U.S. Pat. No. 4,066,802 xerographic means to produce transfer images, mainly for transfer on fabrics are disclosed. Although the main interest of this disclosure is the decoration of fabrics, it is disclosed that the pictures may be transferred to other substrates e.g. glass, metal, synthetic and natural materials.
In U.S. Pat. No. 4,064,285 a printing process in which an image is formed in toner powder by a xerographic method and transferred to a subbing layer on a release material carried by a substrate in sheet form. The image is then heated in contact with a fabric, wood or polymeric material and the substrate coated with release material is removed. The subbing layer is a low-melting polymer selected from vinyl or vinylidene chloride, vinyl acetate, methyl-, ethyl- or butylmethacrylate or their mixtures or copolymers. The release material is a silicon or fluorinated polymer and the substrate is preferably paper. The process of this disclosure is used to print individual pictures, letters, words, etc. on fabrics, garments, household articles, furniture etc. Materials can be decorated with personalised images in full colour at low cost by a simple process using known xerographic methods and equipment. The images of this disclosure are said to be permanent, adhere well and flexible.
In JP-A-63 296982 an electro(stato)graphic method for producing coloured transfer images for transfer onto any material, e.g., thick paper, ultra thin paper, film, acrylic plate, metal plate, etc. The system is said to be less costly than conventional transfer lettering. However the method uses two foils, a first one whereon an electro(stato)graphic transfer image is printed, the transfer image is then transferred to a second (thin) foil and this foil is used to decorate the object.
In U.S. Pat. No. 4,216,283 a xerographic process comprises first depositing an electrostatic image, xerographically, onto a master dry transfer carrier sheet which is adhesive with respect to the developed image. The electrostatic image is developed with a dry toner composition containing a thermoplastic agent, to give an image which is pressure-transferable to a receptor surface. The top surface of the developed image is then contacted with the receptor surface and pressure is applied to the non-image-bearing side of the carrier sheet to transfer the image to the receptor surface. Transfer sheets bearing the required symbols can be made as and when required, and transferred to a wide variety of substrates in the usual way by pressure on the back of the transfer sheet.
In EP-A-466 503, an image carrier sheet for use in image transfer processes is disclosed. The sheet has a flexible web base carrying in order (1) a surface layer of polymeric material, and (2) a thermoplastic coating which is receptive to toner. A toner image is formed xerographically on the thermoplastic coating. The sheet carrying the image is then assembled with a receiving substrate of textile material and subjected to heat and pressure. The thermoplastic coating separates from the polymeric surface layer so that the toner image transfers to the textile substrate, wetting the substrate and flowing into intimate contact with the fibres. The disclosure is interested especially in a transfer method for printing T-shirts. The image on the transfer sheet may be semi-permanent enabling the sheet to be handled without damaging the image.
In WO-A-90 13063 a method of pattern transfer has the pattern reproduced from an original by an electrostatic or preferably a digital laser photocopier onto a transfer sheet is then juxtaposed to an adhesive, moulding or lacquer layer covering the foil. The transfer sheet is peeled off and the dry toner particles are pressed onto the outside or inside of a display window or similar image carrier, which is not necessarily plane. The method is said to be useful for the production of simple textiles, plastics, and ceramics similar artefacts, producing fast and sharp decoration on highly curved surfaces without recourse to harmful solvents.
In DE-C-39 43 556 a method of pattern transfer is disclosed having the pattern reproduced from an original by an electrostatic or preferably a digital laser photocopier onto a transfer sheet. The pattern is then juxtaposed to an adhesive, moulding or lacquer layer covering the foil. The transfer sheet is peeled off and the dry toner particles are pressed onto the outside or inside of a display window or similar image carrier, which is not necessarily plane. The method is said to be very suitable for decoration of simple textiles, plastics, and ceramics similar artefacts. The method is said to produce fast and sharp decoration on highly curved surfaces without recourse to harmful solvents.
Using the electro(stato)graphic methods above do give the possibility to produce personalised printing using hot-stamping foils, but the toner image that is transferred can be damaged when the toner particles forming the image did, during the fixing of the image, not melt into each other so that no continuous film of toner particles is transferred.
In EP-A-453 256 a transfer foil to be imaged by an electro(stato)graphic process is disclosed. The transfer foil comprises a support, a release layer, and a transferable adhesive layer secured on the release layer. The toner particles adhere on the adhesive layer and during transfer, the image is adhered to the object to be decorated by the adhesive layer which together with the image and the release layer is transferred as a whole to the image. In this case the release layer and the adhesive layer form a kind of protective layer over the image, but this can have a detrimental effect since on the areas of the substrate to be decorated where no image is expected toner receiving layer is deposited that can impair the hue, the surface relief, etc. of the substrate that can be decorated.
Therefore further transfer foils useful in the production of transfer images by deposition of electrostatic toner particles on the foil and methods for using the same are still desirable.